Process and apparatus for predicting the tool wear characteristics of metal sheet

ABSTRACT

A process and apparatus for predicting the tool wear characteristics of metal sheet. A test sample of metal sheet having a lubricated metal surface is contacted by a hardened steel ball under a given load. The test sample is rotated and the steel ball is reciprocated back and forth in a substantially linear direction across the test surface, preferably simultaneously for a given period of time. The degree of wear on the metal ball after rotation of the sample and reciprocation of the ball have ceased is an indication of the tool wear characteristics of the metal sheet. Preferably, the degree of wear is determined by optical examination using a microscope to see if abrasion or polishing of the surface of the ball has occurred.

United States Patent [191 v Brauer 1 Sept. 10, 1974 75 Inventor: Dennis R. Brallel', Black Jack, Mo.

[73] Assignee: Olin Corporation, New Haven,

Conn.

[22] Filed: Aug. 22, 1972 [21] App]. No.: 282,671

[52] US. Cl. 73/7 [51] Int. Cl. G0ln 3/56 [58] Field of Search 73/7, 9, 10, 432 R [56] References Cited UNITED STATES PATENTS 2,113,290 4/1938 Benjamin 73/7 2,785,566 3/1957 Mirns 73/9 2,822,686 2/l958 Campana.... 73/7 2,962,890 12/1960 Borrino 73/7 3,011,334 12/1961 Gjertsen 73/7 3,688,556 9/1972 Bigelow 73/7 143,749 2/1931 Germany 73/7 Primary ExaminerRichard C. Queisser Assistant Examiner Daniel M. Yasich Attorney, Agent, or FirmRobert H. Bachman 57 ABSTRACT A process and apparatus for predicting the tool wear characteristics of metal sheet. A test sample of metal sheet having a lubricated metal surface is contacted by a hardened steel ball under a given load. The test sample is rotated and the steel ball is reciprocated back and forth in a substantially linear direction across the test surface, preferably simultaneously for a given period of time. The degree of wear on the metal ball after rotation of the sample and reciprocation of the ball have ceased is an indication of the tool wear characteristics of the metal sheet. Preferably, the degree of wear is determined by optical examination using a microscope to see if abrasion or polishing of the surface of the ball has occurred.

15 Claims, 9 Drawing Figures mmrruswmw 3.834.219

SHEET 1 UF- 2 PROCESS AND APPARATUS FOR PREDICTING THE TOOL WEAR CHARACTERISTICS OF METAL SHEET BACKGROUND OF THE INVENTION This invention relates to a process and apparatus for predicting the tool wear characteristics of metal sheet. Metal sheet can cause excessive tool wear during forming as by stamping, drawing and other similar processes because of the abrasive nature of the particular lot of metal. For a given alloy, for example, copper and copper base alloys, particularly, phosphor bronze, it is possible that metal sheet prepared at different times under different conditions may exhibit differences in its abrasive nature making it suitable or unsuitable for use in terms of its effect on tool life. Therefore, a test is desirable which can be performed on metal sheet to determine its tool wear characteristics.

SUMMARY OF THE INVENTION In accordance with this invention, a tool wear test and apparatus for carrying out the test has been developed which provides a reliable and reproducible means for determining whether a given lot of metal sheet or strip will cause excessive tool wear in forming operations.

The process or test for measuring the tool wear characteristics of the metal sheet comprises providing a test sample of the sheet followed by applying a lubricant to a test surface of the sample. A hardened steel ball is placed in contact with the test surface of the sample and a given load is applied to the ball. The sample is then rotated at a given speed about an axis perpendicular to the plane of the sheet and the steel ball is reciprocated back and forth a given distance at a given speed in a substantially linear direction across the test surface. The rotation of the sample and reciprocation of the ball are continued for a given period of time after which the surface of the ball which contacted the sample is examined to measure the degree of wear on the metal ball.

The test may be performed under any desired set of conditions which preferably enable it to be used as a go-no go test based on whether or not a noticeable polishing effect on the surface of the ball can be observed. The ball is preferably examined under a microscope to determine whether this polishing effect has occurred.

The test should also be adapted to measure the amount of metal build up to be expected on the tools. Metal build up results in a spot on the ball containing metal from the sheet. The diameter of this spot can be measured and should be an indication of the degree of metal build up to be expected when the sheet is formed by conventional methods.

The apparatus for carrying out the test of this invention comprises a means for supporting a test sample of metal sheet having a lubricated test surface, a hardened steel ball contacting the test surface of the sample, means for applying a given load to the ball, means for rotating the sample at a given speed for a given period of time about an axis perpendicular to the plane of the sheet, means for reciprocating the ball back and forth a given distance at a given speed for a given period of time in a substantially linear direction across the test surface.

Preferably in accordance with this invention, the metal ball is a Rockwell Hardness Tester ball penetrator such as set forth in ASTMStandard E 18-67. The advantage of using a Rockwell ball penetrator is that the balls are of a highly uniform character as far as hardness and size which improves the reproducibility and reliability of the process and apparatus of this invention.

The large number of variables such as speed of rotation and reciprocation. sample sizes, reciprocating stroke and time of reciprocation and rotation all of which may be fixed for a given provide a great deal of versatility for adapting the test of this invention to a wide variety of materials.

Therefore, it is an object of this invention to provide a process for measuring the tool wear characteristics of metal strip having improved reliability and reproducibility.

It is a further object of this invention to provide an apparatus for testing the tool wear characteristics of metal sheet.

It is a further object of this invention to provide an apparatus as above wherein a Rockwell ball penetrator is employed so as to provide consistent tool wear test results.

It is a further object of this invention to provide a process and apparatus for measuring the metal build up characteristics of metal sheet on tools.

Other objects and advantages will become apparent as a detailed description proceeds with reference to the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG' 1 is a partial cross sectional view of an apparatus in accordance with this invention.

FIG. 2 is a partial cross sectional view along line 2-2 in FIG. 1 of the apparatus of FIG. 1.

FIG. 3 is a top view of the apparatus in FIG. 1.

FIGS. 4A and 4B shows top and side views, respectively, of a sample holder in accordance with this invention.

FIG. 5A and 5B show top and side cross sectional views, respectively, of a sample retaining nut in accordance with this invention. FIGS. 6A and 6B show top and side views, respectively, of a tool adapted to tighten the sample retaining nut about the sample holder.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In accordance with this invention a process and apparatus for predicting the tool wear characteristics of metal strip is provided having improved reliability and reproducibility.

It is known that an abrasive surface on metal strip can cause excessive tool wear in metal forming operations. This invention provides a process and apparatus for determining the abrasive nature of the surface of metal strip by determining the amount of abrasion on a standard specimen under fixed conditions.

Referring now to the drawings and particularly to FIGS. 1 to 3, there is shown an exemplary apparatus 1 for carrying out the process of this invention. The apparatus I shown is merely a preferred embodiment of this invention and is not meant to be limitive of the invention.

The apparatus 1 is uniquely adapted for use in conjunction with a conventional metallographic type polishing apparatus 2 such as the variable speed model manufactured by Buehler, Ltd. Evanston, Ill. The polishing apparatus 2 shown in phantom in FIG. 1 provides the means for rotating the test sample 3 at a given speed.

The polishing wheel, not shown, has been removed from the tapered spindle 4 of the polishing apparatus 2 motor. A test sample holder 5 has been fitted about the spindle 4. The sample holder 5 includes a tapered bore 6 which is adapted to snugly fit about the tapered spindle 4. The sample holder 5 also includes a slot 7 which is adapted to receive the pin 8 which is attached to the spindle 4 and which prevents relative rotation between the spindle 4 and the sample holder 5.

The sample holder 5 will be described in more detail hereinafter with respect to FIGS. 4A-6B.

The test ball carriage assembly 9 is supported by a base plate 10 having a circular periphery l1 and a shoulder 12 which is adapted to fit about the well 13 of the polishing apparatus 2 and be supported by the lip 14 of the polishing apparatus 2. Preferably, there is a close fit between the base plate 10 and the lip 14 of the polishing apparatus 2 so that the base plate 10 will not move around during the test.

A pair of spaced apart parallel guide members 15 are secured to the base plate 10 by screws 16. Each guide member 15 has a slide groove 17 in a side surface with the groove 17 in one guide member 15 facing the groove 17 in the opposing guide member 15. The grooves 17 in the guide members 15 are so oriented as to be adapted to receive in the sliding engagement a carriage plate 18.

The carriage plate 18 is supported by the guide members 15 and is adapted to slide back and forth within the grooves 17. The carriage plate 18 forms part of the test ball carriage assembly 9 which is adapted to move back and forth in a linear direction and maintain a test ball 22 under a specified load in contact with a test surface 19 of the sample 3. The carriage assembly 9 further includes guide rods 20. The test ball carrying frame 21 is in sliding engagement with the rods and is adapted to move the test ball 22 in and out of contact with the test surface 19.

Bushings 23 are interposed between the ball carrying frame 21 and the guide rods 20 to provide free movement of the frame 21 along the guide rods 20. The bushings 23 are secured to the frame 21 by means of nuts 24.

The frame 21 includes a centrally disposed yoke portion 25. A post 26 having a threaded end portion 27 is secured to the top portion 28 of the yoke by being screwed into a threaded hole 29 in the yoke. The bottom portion 30 of the yoke 25 has a bore 31 which is adapted to receive a ball chuck 32 for carrying the test ball 22. A set screw 33 is provided in the side of the bottom portion 30 of the yoke 25 to provide a means for retaining the ball chuck 32 in place.

The ball chuck 32 comprises a member 34 having a first portion of a diameter adapted to extend into the bore 31 of the yoke 25 and a threaded portion of larger diameter having a concave end surface, not shown, adapted to receive the test ball 22. The test ball 22 is held in place against the concave end surface of the member 34 by means of a retaining sleeve 35 which is adapted to be screwed onto the threaded portion of the member 34. The retaining sleeve 35 has a hole of a diameter less than that of the ball 22 through which the ball 22 protrudes when locked in place.

One or more weights 36 having a donut like shape are placed about the post 26 and are supported by the top surface of the yoke 25.

These elements of the test ball carriage assembly provide the means for contacting the test surface 19 with the test ball 22 and means for applying the load to said test ball. The load comprises the one or more weights 36 and the weight of the carriage assembly 9 less frictional forces and the weight of the plate 18 and rods 20.

The sample holder 5 when fitted about the spindle 4 of the polishing apparatus 2 provides the means for supporting the test sample 3 and the means for rotating the test sample 3 at a given speed about an axis perpendicular to the plane of the sheet of the test sample.

It is also essential in accordance with the apparatus of this invention that means be provided for reciprocating the ball back and forth a given distance at a given speed in a substantially linear direction across the test surface 19.

This means 37 for reciprocating the test ball includes the test ball carriage assembly 9 and a linkage 38 connecting the carriage plate 18 to a reciprocating motor 39 of well known conventional design. The reciprocating motor 39 has adjustments which enable the length of the stroke to be adjusted. The stroke, as the term is employed herein, refers to the span between the end points of a complete back and forth cycle of the motor 39. The reciprocating motor 39 also includes means for varying its speed so that any desired time percycle can be selected.

It is essential in carrying out the process of this invention that a lubricant be applied to the test surface 19 of the sample 3. The test surface 19 may be lubricated in any desired manner. In accordance with the embodiment shown the oil was applied using a conventional oil can. The oil is applied before or after the sample holder 5 containing the sample 3 is placed over the spindle 4 of the polishing apparatus 2 and before the test ball carriage assembly 9 has been moved into its operable position.

Various means for determining or measuring the degree of wear on the test ball 22 can be employed. A preferred means for determining the degree of wear employs a conventional microscope at a given magnification as for example 100 diameters. The surface of the test ball 22 which engaged the sample 3 is viewed through the microscope and any polished or abraded portions on the test ball 22 are noted and are indicative of the wear effect of the metal sheet being tested as will be more fully described hereinafter. Other means for determining the degree of wear on the test ball 22 could be employed as for example, the use of an optical comparitor to check for out of roundness due to wear. Similarly, rolling the test ball 22 down an inclined plane could be employed. If the ball takes a straight path it is still round whereas if it deviates from a straight path,

' it is out of round due to wear. Other techniques could readily be devised and the aforenoted examples are not meant to be limitive of the invention.

The microscope technique is preferred, however, since it permits a given test ball 22 to be used in a plurality of tests by adjusting the ball 22 within the chuck 32 so that a different portion of the ball surface engages the sample 3 for each test.

Referring again to the sample holder 5, it is shown in more detail in FIGS. 4A, 43, 5A and 58. FIGS. 4A and 4B show the sample holder comprises a substantially cylindrical member with a tapered bore 6 extending in from one end and a threaded portion 41 of reduced diameter adjacent the opposing end, with the face 42 of the threaded portion 41 being adapted to receive and support a test sample 3.

The test sample 3 is held in place by means of retaining nut 43 which is shown in FIGS. 5A and 5B. The nut 43 has an internally threaded portion 44 adapted to mesh with the threaded portion 41 of the sample holder 5 and an annular shoulder 45 which is adapted to clamp the test sample 3 to the sample holder 5 when the nut 43 is screwed down onto the tool holder 5.

The retaining nut 43 as shown is of a cylindrical design; however, it could have any desired shape as, for example, it could be square or hexagonal to enable it to be tightened by means of conventional wrenches. The nut 43 as shown has a plurality of holes 46 annularly spaced about its top surface 47. These holes 46 are adapted to receive the pins 48 of the wrench 49 as shown in FIGS. 6A and 6B. The wrench 49 is adapted to tighten and loosen the nut 43 and comprises a T- shaped handle 50 attached to a cylindrical plate 51 having a plurality of pins 48 extending out from the face of the plate opposed to the handle 50. The layout of the pins corresponds substantially to the'layout of the holes 46 in the nut 43.

A cylindrical collar 52 is attached to the plate 51 having an inside diameter just slightly larger than the outside diameter of the nut 43. The wrench 49 as shown is easy to employ since the cylindrical collar 52 aligns the pins 46 about the appropriate hole circle of the nut 43 and a slight rotation of the wrench 49 will seat the pins 48 in the holes 46 of the nut 43.

The process of this invention will now be described with reference to a specific standardized test embodiment. The sheet metal sample 3 may be blanked out on a conventional cupping press with the bottom forming dies removed. In the exemplary standard test, a circular test sample 3 of approximately 1- /2 inches in diameter was employed.

Grit or dirt impressed into or onto the test surface 19 will cause an otherwise satisfactory sample 3 to fail the test. Therefore, preferably care is taken to insure that the sample 3 is clean. This can be accomplished by conventional degreasing and cleaning techniques.

The sample size selected is not meant to be limitive of this invention. Any desired sample size could be used for a given test as long as the stroke of the reciprocating motor 39 is adjusted to the size of the sample 3.

The sample 3 is placed in the sample holder 5 and the sample holder retaining nut 43 is screwed onto the holder 5 to firmly clamp the sample 3 in place. The sample holder 5 is then placed on the spindle 4 of the metallographic polishing apparatus 2.

In the exemplary standard test, a drop of a desired Inbricant, for example, high quality lard oil, was placed on the middle of the test surface 19 by conventional means as, for example, by the use of an oil can. The reciprocating motor 39 was adjusted to have a stroke of about 1 inch with the line of travel of the test ball 22 intersecting the center point of the sample 3.

For smaller samples, the stroke would be cut down; however, the time of reciprocation may be increased to cover the same amount of area. The 1 inch stroke of this example is not meant to be limitive of the invention. A given test may have any desired stroke.

It is preferred in accordance with this invention that the line of travel of the test ball 22 intersect the center point of the sample 3. This is, however, another variable of the test and is not meant to be limitive of the invention. If desired, the line of travel of the test ball 22 may be offset from the center point of the sample 3.

The test ball 22 in accordance with the exemplary standard test was a standard Rockwell /s inch diameter ball penetrator as previously described with reference to the apparatus. The ball was examined before the test under a microscope typically at diameters magnification. The ball should be relatively smooth and show no noticeable imperfections.

The diameter of the test ball may be selected as desired for a given test and the aforenoted exemplary standard test diameter is not meant to be limitive of the invention. Other balls can be used so long as they have a minimum hardness of Rockwell C50.

The use of a standard Rockwell ball penetrator is preferred as aforenoted because of the uniformity required by the Rockwell test standards and the high hardness of 830 VHN (Vickers Hardness Number). For economy, the ball 22 may be used for more than one test by rotating it in the ball chuck 32 so that an unused spot contacts the test surface .19.

In accordance with the exemplary standard test being described, 300 gram weights 36 were employed and the test ball 22 and carrying frame weighed an additional 900 grams. Therefore, the total load for the standard test was approximately 1200 grams. However, larger or smaller weights 36 may be used as desired for other tests and purposes.

The metallographic polishing apparatus 2 is adapted to rotate the sample holder 5 at speeds from about I00 to 1,200 rpm. For the exemplary standard test a speed of 200 rpm was employed. Other speeds could be used as desired for a given test.

The time of the exemplary standard test was selected to be 20 seconds although longer or shorter periods could be used for other tests. Preferably, in accordance with this invention the rotation of the sample 3 and the reciprocation of the test ball 22 take place substantially simultaneously. The speed of the reciprocating motor 39 was set to provide two and one-half back and forth cycles in the 20 second test period. Any desired cycle time could have been employed.

After the test had been completed the Rockwell ball 22 was removed from the apparatus 1 and was examined under a microscope at 100 diameters magnification.

A judgement was made on the acceptability or nonacceptability of the sheet metal with respect to its tool wear characteristics by determining whether or not a spot on the ball 22 has been polished or abraded off. If a polished or abraded spot was present the material in accordance with the parameters of the standard test was deemed to be unacceptable. If no noticeable polishing effect had taken place the material was deemed to be acceptable.

In addition to the aforenoted tool wear indications, it is possible to get some indication of the metal build up to be expected on forming tools during fabircation of the sheet metal from the test of this invention. Metal build up properties are indicated by the formation of a spot of metal from the sheet 3 which is built up on the test ball 22. The diameter of the spot can be measured and should be an indication of the metal build up potential of the sheet 3 being tested.

The exemplary standard test just described is particularly applicable to the evaluation of copper base alloys as, for example, phosphor bronze. For other materials and other alloys the parameters of the test would have to be adjusted to provide the desired test results. It is one of the unique features of this invention that the speed at which the sample 3 is rotated and at which the ball 22 is reciprocated may be varied; that the sample 3 sizes may be varied; and that the time of the test, namely, the time the sample 3 is rotated and the ball 22 reciprocated may be varied.

It is only necessary in accordance with this invention to settle on a given set of parameters as in the aforenoted example for a desired material to thereby provide a standardized test for determining the wear characteristics of the material.

ln accordance with the exemplary embodiment, the degree of wear on the metal ball 22 was determined by examination under a microscope. However, any desired means for determining the degree of wear on the metal ball 22 could be employed.

Preferably in accordance with this invention, the parameters of the aforenoted test are kept within the following ranges. The sample 3 size is preferably from about 1 inch to about 3 inches in diameter and, preferably, the sample is a circular blank. The test ball diameter is preferably from about l/ 16 inch to about /2 inch and is within the tolerances and hardnesses as set forth in ASTM Standard E 18-67 for Rockwell hardness ball penetrators as set forth in Table l7 and 18 thereof.

The stroke of the reciprocating motor 39 and, therefore, the test ball 22 is preferably from about /2 inch to about 2-% inch. The total load which is applied to the test ball 22 is preferably from about 100 grams to about 5,000 grams. The speed at which the sample is rotated is preferably from about 100 to about 1,200 rpm. The speed of reciprocation is preferably from about 0.1 to about 25 seconds per cycle. The test time is preferably from about seconds to about 100 seconds.

Although the preferred lubricant is high quality lard oil, other lubricants may be used and the amount of lubricant employed may be set as desired. Preferably from about one to about five drops of lubricant is employed.

These preferred ranges for the parameters of the tests of the instant invention provide for a wide range of variation in the test; however, by fixing the parameters for a specific test and material, a standardized test can then be employed as in the aforenoted example.

This invention may be embodied in other forms or carried out in other ways without departing from the spirit or essential characteristics thereof. The present embodiment is therefore to be considered as in all respects illustrative and not restrictive, the scope of the invention being indicated by the appended claims, and all changes which come within the meaning and range of equivalency are intended to be embraced therein.

What is claimed is:

l. A process for predicting the tool wear characteristics of metal sheet consisting essentially of:

providing a test sample of metal sheet;

applying a lubricant to a test surface of sheet sample;

contacting said test surface with a hardened steel ball secured in a holder and mounted for reciprocation on a guided plate means;

applying a given load to said ball holder;

rotating said sample at a given speed about an axis perpendicular to the plane of the metal sheet for a given period of time. while substantially simultaneously reciprocating said ball holder back and forth on said guided plate means with a given stroke at a given speed in a substantially linear direction across said test surface for a given period of time; and

determining the degree of wear on the metal ball after said rotating and reciprocating step has been completed.

2. A process as in claim 1 wherein said metal sheet comprises copper or a copper base alloy.

3. A process as in claim 2 wherei nsaidgiyen period of time is from about 5 seconds to about seconds, wherein the speed at which said ball is reciprocated is from about 0.1 to about 25 seconds per back and forth cycle, wherein said load is from about 100 to about 1,500 grams, wherein said sample is rotated at from about 100 to about 1,200 rpm and wherein about one to about five drops of lubricant are applied to said test surface.

4. A process as in claim 3 wherein said sample has a circular periphery and is from about 1 to about 3 inches in diameter, wherein said test ball is from about l/l6 to about /2 inch in diameter, and wherein said stroke is from about Va to about 2% inches.

5. A process as in claim 4 wherein said lubricant comprises a high quality lard oil.

6. A process as in claim 5 wherein said measuring step comprises observing said test ball under a microscope to determine if polishing or abrasion of its surface has occurred.

7. A process as in claim 6 wherein said period of time is about 20 seconds, wherein said speed of reciprocation is about 8 seconds per cycle, wherein said load is about 900 grams, wherein said sample is about 1- /2 inches in diameter, wherein said test ball is about Vs inch in diameter, wherein said stroke is about 1 inch, wherein said speed of rotation is about 200 rpm and wherein one drop of said lubricant is applied.

8. An apparatus for testing the tool wear characteristics of metal sheet comprising:

a first support means for supporting a test sample of metal sheet having a lubricated test surface;

a hardened steel test ball mounted in a slidable holder and contacting said test surface;

a second support means for supporting said ball both in and out of contact with said test surface and for guiding said slidable holder in a reciprocatory man ner;

means connected to said second support means for applying a given load to said ball;

means connected to said first support means for rotating said first support means and said sample at a given speed about an axis perpendicular to the plane of the metal. sheet for a given period of time; and

means connected to said second support means for reciprocating said ball support means back and forth a given stroke at a given speed in a substantially linear direction across said test surface for a given period of time.

9. An apparatus as in claim 8 wherein said test ball has a hardness of at least Rockwell C-scale 50.

10. An apparatus as in claim 9 wherein said test ball comprises a Rockwell Hardness ball penetrator having a diameter of from about A; inch to about /2 inch.

11. An apparatus as in claim 10 wherein said second support means comprises a base plate; a pair of spaced apart parallel guide members secured to said base plate, each guide member having a slide groove in a side surface with the groove in one guide member facing the groove in the other guide member; a carriage plate supported by said guide members and adapted to slide back and forth within said grooves; a plurality of substantially parallel spaced apart guide rods secured to said plate; a test ball carrying frame in sliding engagement with said rods and adapted to move said test ball in and out of contact with said surface; and a ball chuck for holding said ball, said chuck being secured to said ball carrying frame, said ball chuck being adapted to hold said test ball in contacting relationship with said test surface.

12. An apparatus asin claim 11 wherein said means for applying a load to said test ball comprises one or more weights attached to said ball carrying frame.

13. An apparatus as in claim 12 wherein said means for supporting said test sample comprises a sample holder comprising a substantially cylindrical member having a tapered bore extending in from one end and a threaded portion of reduced diameter adjacent the opposing end of the member, said member having a face at its threaded end adapted to receive and support said test sample, said test sample being held in place by a retaining nut which is secured about the threaded portion of said member, said retaining nut having an annular shoulder which is adapted to clamp said test sample to said face of said member.

14. An apparatus as in claim 13 wherein said means for rotating said support means comprises a variable speed motor having a tapered spindle whereby the tapered bore of said sample holder is adapted to engage said tapered spindle.

15. An apparatus as in claim 14 wherein said means for reciprocating said test ball back and forth comprises a reciprocating motor connected to said carriage plate whereby said carriage plate slides back and forth within the grooves of said guide members. 

1. A process for predicting the tool wear characteristics of metal sheet consisting essentially of: providing a test sample of metal sheet; applying a lubricant to a test surface of sheet sample; contacting said test surface with a hardened steel ball secured in a holder and mounted for reciprocation on a guided plate means; applying a given load to said ball holder; rotating said sample at a given speed about an axis perpendicular to the plane of the metal sheet for a given period of time, while substantially simultaneously reciprocating said ball holder back and forth on said guided plate means with a given stroke at a given speed in a substantially linear direction across said test surface for a given period of time; and determining the degree of wear on the metal ball after said rotating and reciprocating step has been completed.
 2. A process as in claim 1 wherein said metal sheet comprises copper or a copper base alloy.
 3. A process as in claim 2 wherein said given period of time is from about 5 seconds to about 100, wherein the speed at which said ball is reciprocated is from about 0.1 to about 25 seconds per back and forth cycle, wherein said load is from about 100 to about 1,500 grams, wherein said sample is rotated at from about 100 to about 1,200 rpm and wherein about one to about five drops of lubricant are applied to said test surface.
 4. A process as in claim 3 wherein said sample has a circular periphery and is from about 1 to about 3 inches in diameter, wherein said test ball is from about 1/16 to about 1/2 inch in diameter, and wherein said stroke is from about 1/2 to about 2- 1/2 inches.
 5. A process as in claim 4 wherein said lubricant comprises a high quality lard oil.
 6. A process as in claim 5 wherein said measuring step comprises observing said test ball under a microscope to determine if polishing or abrasion of its surface has occurred.
 7. A process as in claim 6 wherein said period of time is about 20 seconds, wherein said speed of reciprocation is about 8 seconds per cycle, wherein said load is about 900 grams, wherein said sample is about 1- 1/2 inches in diameter, wherein said test ball is about 1/8 inch in diameter, wherein said stroke is about 1 inch, wherein said speed of rotation is about 200 rpm and wherein one drop of said lubricant is applied.
 8. An apparatus for testing the tool wear characteristics of metal sheet comprising: first support means for supporting a test sample of metal sheet having a lubricated test surface; a hardened steel test ball mounted in a slidable holder and contacting said test surface; a second support means for supporting said ball both in and out of contact with said test surface and for guiding said slidable holder in a reciprocatory manner; means connected to said second support means for applying a given load to said ball; means connected to said first support means for rotating said first support means and said sample at a given speed about an axis perpendicular to the plane of the metal sheet for a given period of time; and means connected to said second support means for reciprocating said ball support means back and forth A given stroke at a given speed in a substantially linear direction across said test surface for a given period of time.
 9. An apparatus as in claim 8 wherein said test ball has a hardness of at least Rockwell C-scale
 50. 10. An apparatus as in claim 9 wherein said test ball comprises a Rockwell Hardness ball penetrator having a diameter of from about 1/8 inch to about 1/2 inch.
 11. An apparatus as in claim 10 wherein said second support means comprises a base plate; a pair of spaced apart parallel guide members secured to said base plate, each guide member having a slide groove in a side surface with the groove in one guide member facing the groove in the other guide member; a carriage plate supported by said guide members and adapted to slide back and forth within said grooves; a plurality of substantially parallel spaced apart guide rods secured to said plate; a test ball carrying frame in sliding engagement with said rods and adapted to move said test ball in and out of contact with said surface; and a ball chuck for holding said ball, said chuck being secured to said ball carrying frame, said ball chuck being adapted to hold said test ball in contacting relationship with said test surface.
 12. An apparatus as in claim 11 wherein said means for applying a load to said test ball comprises one or more weights attached to said ball carrying frame.
 13. An apparatus as in claim 12 wherein said means for supporting said test sample comprises a sample holder comprising a substantially cylindrical member having a tapered bore extending in from one end and a threaded portion of reduced diameter adjacent the opposing end of the member, said member having a face at its threaded end adapted to receive and support said test sample, said test sample being held in place by a retaining nut which is secured about the threaded portion of said member, said retaining nut having an annular shoulder which is adapted to clamp said test sample to said face of said member.
 14. An apparatus as in claim 13 wherein said means for rotating said support means comprises a variable speed motor having a tapered spindle whereby the tapered bore of said sample holder is adapted to engage said tapered spindle.
 15. An apparatus as in claim 14 wherein said means for reciprocating said test ball back and forth comprises a reciprocating motor connected to said carriage plate whereby said carriage plate slides back and forth within the grooves of said guide members. 